The letter read: “We have decided to withdraw your son/daughter from the GCSE Mathematics course and transfer them to Level 1 Essential Skills Numeracy.

“We have taken the decision to change the course as it will enable your child to achieve a recognised qualification that can be built upon should they progress to Southern Regional College of Further Education.”

The parents’ group Education Equality for Lurgan has criticised the governance of the school.

Writing to the Education Authority, the group described it as a “totally unsatisfactory situation”.

“Pupils complained they had no continuity in this particular subject, with up to eight different teachers throughout the year and varying different teaching styles, including teachers that were not even maths teachers,” the group claimed.

The Education Authority said that it did not wish to comment at this time.

However, acting principal Ruth Harkness said: “A decision was made for roughly 10% of our year 12 students to follow an equivalent mathematics course based on individual needs, ultimately improving outcomes for these students.

“This includes Essential Skills Numeracy Level 1 and Level 2, which is tailored to the students’ specific needs.

“We have shaped our curriculum offer to the individual needs of the students to allow them to reach their full potential. This will also create pathways through further/higher education, training and employment.

“I am, along with the board of governors, fully committed to making the right decisions for our students that will empower them to reach their full potential.”

Divided between two sites in Lurgan and Portadown, most of the 579 GCSE pupils at Craigavon are located on the Portadown site.

In March, this paper reported that Craigavon Senior High was 185th out of 191 for GCSE results in Northern Ireland.

Some 26.5% of students at the school achieved five or more GCSEs at grades A* to C.

The school noted that GCSE maths results at Craigavon Senior High School are in line with Northern Ireland’s non-grammar schools.